Gas lift system

ABSTRACT

A gas lift system that operates on a substantially nonvarying casing pressure and employs at least one gas lift device which has a housing for accumulating liquid being displaced to the surface of the well and valve means associated with the housing for admitting liquid to the housing and removing liquid therefrom by way of casing pressure, the valve means associated with the housing being operable by a float means.

United States Patent Robert F. Berry 1 Dallas, Tex.

Appl. No. 823,252

Filed I May 7, 1969 Patented Aug. 17, 1971 Assignee Dresser Industries, Inc. Dallas, Tex.

Inventor GAS LIFI SYSTEM 9 Claims, 2 Drawing Figs.

US. Cl...

Int. Cl

Field 01 Search 417 132 F041 l/06, 041 3 00 1 03/24 x,

References Cited UNITED STATES PATENTS 6/1930 Hardie et al.

Rogers 103/248 1,893,151 1/1933 Rubel..... 103/239 X 2,855,860 10/1958 Crump 103/148 X 3,138,113 6/1964 Arutunofii. 103/239 3,242,873 3/1966 Smith [03/248 Primary ExaminerCarlton R. Croyle Assistant Examiner-R. E. Gluck A!t0rneys-Robert W. Mayer, Daniel Rubin, Peter J. Murphy, Frank S. Troidl, Roy L. Van Winkle, William E. Johnson. Jr. and Roderick W. MacDonald ABSTRACT: A gas lift system that operates on a substantially nonvarying casing pressure and employs at least one gas lift device which has a housing for accumulating liquid being displaced to the surface of the well and valve means associated with the housing for admitting liquid to the housing and removing liquid therefrom by way ofcasing pressure, the valve means associated with the housing being operable by a float means.

PATENTEU AUGIYIQYI 3,600,105

11v VEN TO'R ROBERT F. BERRY FIG. 2

A T TORNE Y GAS LIFT SYSTEM BACKGROUND OF THE INVENTION Heretofore, the maximum depth of lift in a conventional gas lift system has been limited by the casing pressure. As the depth of the well increased the casing pressure had to be increased in order to lift liquid in the tubing the full length of the tubing to the surface of the well. There are, of course, practical and physical limitations on the magnitude of the casing pressure that can be maintained in a well and, therefore, this type of system has its limitations based upon well depth-casing pressure relationships.

SUMMARY OF THE INVENTION According to this invention a gas lift system is employed which does not depend upon increased casing pressure for its operation even though the system is used at progressively deeper well depths. Thus, this invention employs a single, generally low, pressure for its casing pressure no matter what depth in'the well the gas lift device is to operate and the system still lifts liquid in the tubing to the surface of the well.

In the system of this invention there is employed a gas lift device which comprises a housing for receiving and holding liquid transported through the tubing toward the surface of the well, the housing having various apertures for venting the interior of the housing to a zone of low pressure, for admitting liquid to the housing, for admitting casing pressure to the housing, and conduit means for removing liquid from the housing to the tubing, the aperture means being operatively associated with valve means and the valve means being operated by float means.

The gas lift system of this invention utilizes the tubing string and employs at spaced apart positions along the length thereof the gas lift devices described hereinabove.

This invention also relates to a method of removing liquid from a well through a tubing zone utilizing at least one accumulation zone (housing) along the length of the tubing zone and utilizing pressure exterior to the tubing zone (casing pressure) to lift well liquid into the accumulation zone through the tubing zone. The well liquid is collected in the accumulation zone and casing pressure is then admitted to the interior of the accumulation zone to lift the liquid therein to the surface of the well or to the next higher accumulation zone. The process is repeated with any higher accumulation zone or zones until the liquid reaches the surface of the well.

Accordingly, it is an object of this invention to providea new and improved gas lift system. It is another object to provide a new and improved gas lift device. It is yet another object to provide a new and improved gas lift method whereby liquid is lifted from a well at varying depths using a relatively low, substantially nonvarying casing pressure.

Other aspects, objects, and advantages of the invention will be apparent to those skilled in the art from the disclosure and the appended claims.

DETAILED DESCRIPTION OF THE INVENTION FIG. '1 shows an elevational cross section of a well employing the gas lift system of this invention.

FIG. 2 shows a cross section of two gas lift devices employed in the system of FIG. 1.

More specifically, FIG. 1 shows a well bore 1 lined with casing 2, the casing being perforated at 3 to allow the entry of a liquid, e.g., crude oil, from producing zone 4.

The casing pressure on the tubing can be varied as desired by increasing or decreasing the pressure in casing 2 by way of pipe 5 and a conventional pressure pump (not shown).

Inside casing 2 is disposed a conventional tubing string (tubing zone) 6 which carries at spaced-apart points along the length thereof gas lift devices of this invention as denoted by 7. Tubing 6 is in open communication with liquid 9 in the bottom of easing 2 by way of its open end 8 and is in open communication with the surface of the well for removal of liquid from the tubing by way of pipe 10. Pipe 11 communicates with the interior of the tubing and is at atmospheric pressure at the surface of the well by way of its open end 12 thereby venting the interior of tubing 6 through gas lift device 7 to a zone of lower pressure.

FIG. 2 shows cross sections of two of the gas lift devices 7 of FIG. l in their normal operating position on tubing 6 and inside casing 2.

Each gas lift device contains three valve means and a conduit means in the interior thereof, the three valve means and conduit means being spaced from one another around the periphery of tubing 6. For sake of brevity and clarity, the lower gas lift device 7' has been drawn to show one of the valve means and the conduit means while the upper gas lift device 7" has been drawn to show the other two valve means. It should be clearly understood from the outset that device 7 also contains the two valve means shown for device 7' and that device 7" also contains the valve means and conduit means shown for device 7. For example, the two valve means shown in device 7", one behind the structure shown in FIG. 2 and the other extending outwardly from FIG. 2 in front of the structure shown in that figure.

Each device 7' and 7" is composed of a housing or accumulation zone comprising concentric inner and outer annular walls 15 and 16, respectively, that are spaced from one another and joined to one another by upper and lower annular end pieces 17 and 18 respectively. This housing will receive and hold liquid therein until removed therefrom. Inner wall 15 can be formed from tubing 6 or separate therefrom.

The two valve means shown in the device 7" are for admitting liquid to the interior of the housing.

First valve means 20 in 7" is composed of a valve member 21 carried by valve stem 22. Valve stem 22 carries upper and lower arm means 23 and 24, respectively. A first aperture 25 is provided in upper end piece 17 to allow open communication between the interior of the housing and vent means 11. Valve member 21 is adapted to close first aperture 25 when the member is raised into contact with upper end piece 17.

Second valve means 30 is composed of a valve member 31 carried by valve stem 32. Valve stem 32 also carries upper and lower arm means 33 and 34, respectively. Second aperture means 35 openly connects the interior of the housing with the interior of tubing 6 through check valve 36.

Check valve 36 is a conventional structure wherein a resilient means 37 normally biases valve member 38 into the closed position on port 39 to prevent backward flow of liquid from the interior of the housing through second aperture 35 into tubing 6. Thus, liquid inside tubing 6 can pass into the housing through second aperture 35 but not in the reverse direction.

The annular interior of the tubing about vent means 11 is separated, with respect to device 7", into an upper portion 40 and a lower portion 41 by means of annular partition 42. With respect to each device 7 there are upper and lower interior portions in the tubing string which are physically isolated from one another except through the device 7.

Device 7" also contains the third valve means 50 shown in device 7'. Valve means 50 comprises valve member 51 which is carried by valve stem 52. Valve stem 52 also carries upper and lower arm means 53 and 54, respectively. Third aperture 55 communicates through valve seat 56 with the interior of the housing. Thus, by third valve means 50 casing pressure on the interior of easing 2 but on the exterior of tubing 6 can be admitted to the interior of the housing.

Unlike first and second valve means 20 and 30, third valve means 59 is adapted to be opened when its valve stem is raised towards upper end piece 17. Thus, third valve means 50 works oppositely from first and second valve means 20 and 30 so that when first and second valve means 20 and 30 are closed by their valve members 21 and 31 closing first and second apertures 25 and 35, third valve means 50 is opened by its valve member 51 being spaced away from seat 56.

Device 7" also contains conduit means 60 shown extending through partition 42 into a lower portion of the housing of device 7'. This puts the interior of the housing in open communication with the annular interior of tubing 6 by way of check valve means 61.

Check valve means 61 is substantially the same conventional apparatus as check valve means 36 except that resilient means 62 is biased to normally close port 63 by forcing valve member 64 against its seat around port 63. This prevents liquid from flowing backward from the interior of tubing 6 through conduit means 60 into the housing. Thus, liquid can only pass from the interior of device 7" into upper interior portion 40 of tubing 6. As with device 7", device 7 has an upper annular interior portion of tubing 6 (which in this case is portion 41) and a lower annular interior portion 43. Thus, with respect to device 7' upper and lower portions 41 and 43, respectively, are physically isolated from one another by way of partition 42 except through device 7.

Vent means 11 is closed at its bottom end 11' so that except for first aperture 25 for devices 7' and 7" and any other device 7 along the lengths of the tubing 6, vent means 11 is open to the lower pressure that obtains in the atmosphere at the surface ofthe well.

it should be stressed that device 7 contains first and second valve means and 30 and first and second aperture means and 35 as described for device 7". Thus, devices 7' and 7" each contain spaced around the annular interior of each of their housings first, second and third valve means 20, 30, and 5G and their associated apertures, and conduit means 60.

Each device 7 contains a float means 70 which has a plurality of passage means 71 therethrough. Valve stems 22, 32, and 52, and conduit means 60 each extend through one of these passage means. Float means 70 is disposed between the upper and lower arms of each valve stem and is adapted to rise or fall with the rise or fall of the liquid level inside the housing of the devices 7 and 7". Thus, float means 70 is the actuating member for first, second, and third valve means 20, and 50 by way of its abutting the upper and lower arms carried by the valve stems ofeach ofsaid valves.

Float means 70 can be any material which is substantially inert to the liquids and gases prevailing in the well and which will float on the liquids in the well. For example, cork, foamed polymer, hollow metal rings, and the like can be employed.

In operation, liquid 9 in the bottom of easing 2 is forced through the open end 8 of tubing 6 into the lowest device 7. The liquid passes through check valve 36 and second aperture into the interior of the housing of the device 7. Valve 30 and aperture 35 are open during this step because device 7 is substantially empty of liquid and, therefore, float 70 is in the lower portion of device 7 resting against the lower arms 34 of valve stem 32 and thereby forcing valve member 31 away from second aperture 35.

When float 70 opens valve 30 by abutment against lower arms 34, it also opens valve 20 by abutment against lower arms 24. The opening of valve 20 vents the interior ofdevice 7 to the lower atmospheric pressure.

As liquid inside tubing 6 passes through check valve 36 and second aperture 35 into the interior of device 7 and is collected therein, the liquid level in device 7 rises and is collected therein, the liquid level in device 7 rises and float 70 rises,

floating on top of the liquid level.

When float 70 is in the lower portion of device 7 thereby opening valves 20 and 30, it also closes valve 50 by abutting against lower arms 54 and forcing valve member 51 downwardly against seat 56. Thus, although the gas pressure in casing 2 exterior to tubing 6 is forcing liquid 9 into tubing 6 through open bottom end 8, the same gas pressure is not admitted to device 7 because its third valve means 50 is closed.

As the liquid level in device 7 increases by collection of more and more liquid from the interior of tubing 6, float 70 soon rises to an upper portion of device 7 and abuts against the upper arms of valves 20, 30 and 50. When this occurs, valves 20 and 30 are closed by raising valve stems 22 and 32 through third aperture 50 and the aperture defined by seat 56,

and into the interior of device 7.

The casing pressure admitted to the interior of device 7 forced liquid in that device upwardly through conduit means 60 and check valve means 61 into an upper portion of tubing 6 and into the next higher device 7 by way of that devices check valve 36, and second aperture 35.

Thus, liquid is raised by easing pressure from the bottom of the casing into the lowermost device 7 wherein the liquid is collected until the housing of device 7 is substantially liquidfull. At this time float 70 closes valves 20 and 30. Valve 20 need be open only during the filling operation so that there is no pressure buildup in the interior of the device as the liquid level increases in that device. At the same time that communication is cut off between the interior of device 7 and tubing 6, third valve means 50 is opened so that casing pressure gas is admitted to the interior of the device to push the liquid from that device through conduit means 60 and tubing 6 into the next higher device 7 wherein the liquid is again accumulated until the device is full. When the next higher device 7 is full, the third valve means 50 is opened and the liquid again forced out ofthat device into the next higher device 7.

By this method of operation the liquid is stage lifted from one device 7 to the next higher device 7 until it reaches the surface of the well. All of this stage lifting is accomplished with a single casing gas pressure so that, in effect, liquid 9 is lifted from the bottom of casing 2 to the surface of the well using only a single casing gas pressure. This pressure can be a low pressure regardless of the depth of the casing.

Of course, devices 7 must be spaced from one another a distance no greater than the distance which the prevailing casing pressure can lift the liquid in the tubing. This spacing will vary widely depending upon the casing pressure, the density of the liquid being lifted, the size of the tubing, and so on, but will be readily ascertainable by those skilled in the art when the specific operating conditions are known.

If there is a relatively shallow well, a single device 7 may be sufficient so that liquid is raised from the bottom of the casing to the single device 7 and from that device to the surface of the well. However, for deeper wells, two or more vertically spaced-apart devices 7 may be used. For example, three spaced-apart devices 7 may be used as shown in FIG. 1 although more can be employed if necessary.

Although check valves 36 and 61 are shown in FIG. 2 in the interior of tubing 6, they can be readily adapted in a manner obvious to those skilled in the art to reside in the interior of the device 7 so that the device can be mounted on tubing 6 without any check valve apparatus extending into the interior of the tubing.

As can be seen from the above, this invention relates to a method for removing liquid from a well through a tubing zone 6 by utilizing at least one accumulation zone 7 aiong the length of the tubing zone and applying pressure to the liquid 8 in the well to lift the liquid into the tubing zone and then into the accumulation zone. After collecting sufficient liquid in the accumulation zone, pressure is admitted to the accumulation zone to lift the liquid therein to the surface of the well or to the next higher accumulation zone. If the liquid is lifted to a next higher accumulation zone, the process is repeated with this next higher accumulation zone and any higher accumulation zone or zones until the liquid is finally stage lifted to the surface of the well.

in carrying out the process of this invention, the operational parameters, as pointed out above, can vary widely depending upon the liquids present in the well, the depth of the well, the operational pressures available at that specific well, and the like. Generally, the casing pressures employed in this invention can vary from about to about 1,000 p.s.i.g. and the vertical spacing between a device 7 and the next higher device 7, should there be one, will generally be from about 200 to about 2,000feet. Each device 7 can be made to contain from about 0.25 to about 1 barrel (42 US. gallons) of liquid.

Thus, in a well 2,000 feet deep with a casing pressure of 500 p.s.i.g., one device 7 can be employed 1,000 feet from the bottom of the well (1,000 feet from the surface of the well) and the 500 p.s.i.g. casing pressure will then lift crude oil at the bottom of the well to the device 7. When the device 7 is'substantially full of oil, and its third valve means 50 opened to the 500 p.s.i.g. casing pressure, the casing pressure admitted thereinto will raise the oil therein to the surface of the well. Because device 7 operates on a float mechanism, the operation is automatic and whenever device 7 becomes sufficiently liquid full to open third valve means 50, the oil therein will be automatically lifted to the surface of the well. The automatic operation feature of this invention applies whether there is one or several devices 7 along the length of the tubing string.

This invention, although described with respect to external casing pressure provided through pipe 5 of FIG. 1, can utilize only formation gas pressure that is already present in the well from formation 4. Also, a combination of external pressure from pipe 5 and internal formation gas pressure can be utilized..No matter what the source of the gas pressure, the casing pressure is utilized by this invention with 100 percent efficiency even though the casing pressure is too low to lift the liquid from the bottom of the well to the surface in a single lifting operation.

Each lifting device of this invention can operate independent of any other devices present in the same tubing string even though each device is under the same casing pressure. This is a further advantageous feature in that each device 7 is working at all times and, therefore, constant removal of liquid from the bottom of the well bore to the surface of the well is insured.

Reasonable variations and modifications are possible within the scope of this disclosure without departing from 'the spirit and scope of this invention.

The embodiments of the invention in which 1 claim an exclusive property or privilege are defined as follows:

1. A gas lift device adapted for lifting liquid through tubing in a well comprising a hollow annular housing adapted for mounting on said tubing for receiving and holding liquid therein, said housing having first aperture means for renting the interior of said housing to a zone of low pressure, p g second aperture means for admitting liquid to saidhousing from the interior of said tubing,

third aperture means for admitting gas to said housing from the well annulus exterior of said tubing, and

conduit means for removing liquid from said housing to the interior of said tubing, first, second, and third valve means associated with said first, second, and third aperture means, respectively,

annular float means carried in said housing and adapted to operate said first, second, and third valve means so that said first and second valve means are closed and said third valve means is opened when said float means is in a first position in said housing and said first and second valve means are opened and said third valve means is closed when said float means is in a second position in said housing which is different from said first position.

2. The device according to claim 1 wherein said conduit means carries a check valve means to prevent backfiow of liquid into said housing through said conduit means.

3. The device according to claim 1 wherein said housing has concentric inner and outer annular walls that are spaced from one another and joined to one another by upper and lower annular end pieces, said first, second, and third aperture means communicate with the housing through said upper end piece, said conduit means extends through said housing into a lower portion thereof for substantially complete removal of liquid from said housing through said conduit means, said first,

second and third valve means comprise first, second, and third valve members carried on first, second, and third valve stems, respectively, said first and second valve members being adapted to close their associated aperture means in said upper end piece when their respective valve stems are raised, said third valve means being adapted to close its associated aperture means in said upper end piece when its valve stem is lowered, each said valve stem extending downwardly in the interior of said housing, said float means being annular and having passage means therethrough, each said valve stem and said conduit means extending through said passage means in said float means, upper and lower arm means carried on each of said valve stems and on opposite sides of said float means so that when said float means rises towards said upper end piece it abuts said upper arms and closes said first and second valve means while opening said third valve means, and so that when said float means is lowered towards said lower end piece it abuts said lower arms and closes said third valve means while opening said first and second valve means.

4. The device according to claim 3 wherein check valve means are associated with said second aperture means and said conduit means, said check valve means with said second aperture means preventing the flow of liquid from out from the interior of said housing, said check valve means with said conduit means preventing the flow of liquid into said housing through said conduit means.

5. In a gas lift system wherein liquid is removed from a well through a tubing means, the improvement comprising said tubing carrying at least one device of claim 1, said second aperture means of said device of claim 1 communicating with an interior portion of said tubing which is lower than said device, said conduit means of said device of claim 1 communicating with an interior portion of said tubing which is higher than said device, said lower and higher interior portions of said tubing being physically isolated from each other except through said device of claim 1, said third aperture means of said device of claim 1 communicating with the environment exterior to said tubing, and second conduit means carried by said tubing and openly connecting said first aperture means of said device of claim 1 with a zone of pressure lower than the pressure in the housing of said device.

6. The system according to claim 5 wherein said second conduit means is carried interiorly and concentrically of said tubing, and said zone of lower pressure is one of the atmosphere at the surface of the earth and a low pressure gas system.

7. In a gas lift system wherein liquid is removed from a well through a tubing means, the improvement comprising said tubing carrying at least one device of claim 2, said second aperture means of said device of claim 2 communicating with an interior portion of said tubing which is lower than said device, said conduit means of said device of claim 2 communicating with an interior portion of said tubing which is higher than said device, said lower and higher interior portions of said tubing being physically isolated from each other except through said device of claim 2, said third aperture means of said device of claim 2 communicating with the environment exterior to said tubing, and second conduit means carried by said tubing and openly connecting said first aperture means of said device of claim 2 with a zone of pressure lower than the pressure in the housing of said device.

8. In a gas lift system wherein liquid is removed from a well through a tubing means, the improvement comprising said tubing carrying at least one device of claim 3, said second aperture means of said device of claim 3 communicating with an interior portion of said tubing which is lower than said device, said conduit means of said device of claim 3 communicating with an interior portion of said tubing which is higher than said device, said lower and higher interior portions of said tubing being physically isolated from each other except through said device of claim 3, said third aperture means of said device of claim 3 communicating with the environment exterior to said tubing, and second conduit means carried by said tubing and openly connecting said first aperture means of said device of claim 3 with a zone of pressure lower than the pressure in the housing of said device.

9. In a gas lift system wherein liquid is removed from a well through a tubing means, the improvement comprising said tubing carrying at least one device of claim 4, said second aperture means of said device of claim 4 communicating with an interior portion of said tubing which is lower than said device, said conduit means of said device of claim 4 communicating with an interior portion of said tubing which is higher 

1. A gas lift device adapted for lifting liquid through tubing in a well comprising a hollow annular housing adapted for mounting on said tubing for receiving and holding liquid therein, said housing having first aperture means for renting the interior of said housing to a zone of low pressure, second aperture means for admitting liquid to said housing from the interior of said tubing, third aperture means for admitting gas to said housing from the well annulus exterior of said tubing, and conduit means for removing liquid from said housing to the interior of said tubing, first, second, and third valve means associated with said first, second, and third aperture means, respectively, annular float means carried in said housing and adapted to operate said first, second, and third valve means so that said first and second valve means are closed and said third valve means is opened when said float means is in a first position in said housing and said first and second valve means are opened and said third valve means is closed when said float means is in a second position in said housing which is different from said first position.
 2. The device according to claim 1 wherein said conduit means carries a check valve means to prevent backflow of liquid into said housing through said conduit means.
 3. The device according to claim 1 wherein said housing has concentric inner and outer annular walls that are spaced from one another and joined to one another by upper and lower annular end pieces, said first, second, and third aperture means communicate with the housing through said upper end piece, said conduit means extends through said housing into a lower portion thereof for substantially complete removal of liquid from said housing through said conduit means, said first, second and third valve means comprise first, second, and third valve members carried on first, second, and third valve stems, respectively, said first and second valve members being adapted to close their associated aperture means in said upper end piece when their respective valve stems are raised, said third valve means being adapted to close its associated aperture means in said upper end piece when its valve stem is lowered, each said valve stem extending downwardly in the interior of said housing, said float means being annular and having passage means therethrough, each said valve stem and said conduit means extending through said passage means in said float means, upper and lower arm means carried on each of said valve stems and on opposite sides of said float means so that when said float means rises towards said upper end piece it abuts said upper arms and closes said first and second valve means while opening said third valve means, and so that when said float means is lowered towards said lower end piece it abuts said lower arms and closes said third valve means while opening said first and second valve means.
 4. The device according to claim 3 wherein check valve means are associated with said second aperture means and said conduit means, said check valve means with said second aperture means preventing the flow of liquid from out from the interior of said housing, said check valve means with said conduit means preventing the flow of liquid into said housing through said conduit means.
 5. In a gas lift system wherein liquid is removed from a well through a tubing means, the improvement comprising said tubing carrying at least one device of claim 1, said second aperture means of said device of claim 1 communicating with an interior portion of said tubing which is lower than said device, said conduit means of said device of claim 1 communicating with an interior portion of said tubing which is higher than said device, said lower and higher interior portions of said tubing being physically isolated from each other except through said device of claim 1, said third aperture means of said device of claim 1 communicating with the environment exterior to said tubing, and second conduit means carried by said tubing and openly connecting said first aperture means of said device of claim 1 with a zone of pressure lower than the pressure in the housing of said device.
 6. The system according to claim 5 wherein said second conduit means is carried interiorly and concentrically of said tubing, and said zone of lower pressure is one of the atmosphere at the surface of the earth and a low pressure gas system.
 7. In a gas lift system wherein liquid is removed from a well through a tubing means, the improvement comprising said tubing carrying at least one device of claim 2, said second aperture means of said device of claim 2 communicating with an interior portion of said tubing which is lower than said device, said conduit means of said device of claim 2 communicating with an interior portion of said tubing which is higher than said device, said lower and higher interior portions of said tubing being physically isolated from each other except through said device of claim 2, said third aperture means of said device of claim 2 communicating with the environment exterior to said tubing, and second conduit means carried by said tubing and openly connecting said first aperture means of said device of claim 2 with a zone of pressure lower than the pressure in the housing of said device.
 8. In a gas lift system wherein liquid is removed from a well through a tubing means, the improvement comprising said tubing carrying at least one device of claim 3, said second aperture means of said device of claim 3 communicating with an interior portion of said tubing which is lower than said device, said conduit means of said device of claim 3 communicating with an interior portion of said tubing which is higher than said device, said lower and higher interior portions of said tubing being physically isolated from each other except through said device of claim 3, said third aperture means of said device of claim 3 communicating with the environment exterior to said tubing, and second conduit means carried by said tubing and openly connecting said first aperture means of said device of claim 3 with a zone of pressure lower than the pressure in the housing of said device.
 9. In a gas lift system wherein liquid is removed from a well through a tubing means, the improvement comprising said tubing carrying at least one device of claim 4, said second aperture means of said device of claim 4 communicating with an interior portion of said tubing which is lower than said device, said conduit means of said device of claim 4 communicating with an interior portion of said tubing which is higher than said device, said lower and higher interior portions of said tubing being physically isolated from each other except through said device of claim 4, said third aperture means of said device of claim 4 communicating with the environment exterior to said tubing, and second conduit means carried by said tubing and openly connecting said first aperture means of said device of claim 4 with a zone of pressure lower than the pressure in the housing of said device. 